1. Field of the Invention
The present invention relates to a multilayer wiring board and its manufacturing method; more specifically, a multilayer wiring board with built-in electronic components such as an IC and its manufacturing method.
2. Discussion of the Background
Portable information devices (so-called mobile data terminals) are becoming more compact and highly functional. As for a multilayer printed wiring board with built-in semiconductor elements, for example, Japanese Laid-Open Patent Publication 2001-339165 and Japanese Laid-Open Patent Publication 2002-050874 describe multilayer printed wiring boards structured with a semiconductor element, insulation layers formed on a substrate so as to cover the semiconductor element, conductive circuits formed on the surfaces of the insulation layers, and via holes formed in the insulation layers to electrically connect the conductive circuits and the pads on the semiconductor element.
In such multilayer printed wiring boards, external connection terminals (such as a PGA or BGA) are formed on the outermost surface and the built-in semiconductor element in the substrate is electrically connected to the outside through those external connection terminals.
Also, Japanese Laid-Open Patent Publication 2001-274034 describes electronic-component packaging technology and high-density mounting of electronic components along with a shielding effect on electronic components from electromagnetic noise. Japanese Laid-Open Patent Publication 2001-274034 describes an electronic-component package which has: a concave portion formed in the core material; a semiconductor chip embedded in the concave portion; an insulation layer formed on the surface of the core material that is on the opening side of the concave portion to cover the concave portion; a wiring layer formed on the surface of the insulation layer; and vias formed in the insulation layer and electrically connecting the wiring layer and electrode terminals formed on the surface of the semiconductor chip that is on the opening side of the concave portion. In such an electronic-component package, the inner walls and the bottom of the concave portion are structured with conductive metal.
Furthermore, Japanese Laid-Open Patent Publication 2006-019342 describes that harmonic radiation noise may be isolated and reflection of such noise may be substantially reduced. Noise suppression may be achieved by structuring a metal shield which covers a semiconductor IC embedded in a multilayer substrate and covers a surface of the multilayer substrate, and having a magnetic sheet disposed between the surface of the multilayer substrate and the metal shield.
The contents of those publications are incorporated herein by reference in their entirety.